From: David Miller <davem@davemloft.net>
To: akpm@osdl.org
Cc: dmonakhov@openvz.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm:D-cache aliasing issue in cow_user_page
Date: Thu, 19 Oct 2006 00:22:37 -0700 (PDT) [thread overview]
Message-ID: <20061019.002237.130236131.davem@davemloft.net> (raw)
In-Reply-To: <20061019001747.7da58920.akpm@osdl.org>
From: Andrew Morton <akpm@osdl.org>
Date: Thu, 19 Oct 2006 00:17:47 -0700
> On Thu, 19 Oct 2006 00:00:27 -0700 (PDT)
> David Miller <davem@davemloft.net> wrote:
>
> > Unfortunately, the kernel has just touched the page and thus there are
> > active cache lines for the kernel side mapping. When we map this into
> > user space, userspace might see stale cachelines instead of the
> > memset() stores.
>
> hm. Has it always been that way or did something change?
Always.
> > Architectures typically take care of this in copy_user_page() and
> > clear_user_page(). The absolutely depend upon those two routines
> > being used for anonymous pages, and handle the D-cache issues there.
>
> Only anonymous pages? There are zillions of places where we modify
> pagecache without a flush, especially against the blockdev mapping (fs
> metadata).
It's cpu stores that matter, not device DMA and the like, and we have
flush_dcache_page() calls in the correct spots. You can see that
we take care of this even in places such as the loop driver :-)
WARNING: multiple messages have this Message-ID (diff)
From: David Miller <davem@davemloft.net>
From: Andrew Morton <akpm@osdl.org>
To: akpm@osdl.org
Cc: dmonakhov@openvz.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm:D-cache aliasing issue in cow_user_page
Date: Thu, 19 Oct 2006 00:22:37 -0700 (PDT)
Date: Thu, 19 Oct 2006 00:17:47 -0700 [thread overview]
Message-ID: <20061019.002237.130236131.davem@davemloft.net> (raw)
In-Reply-To: <20061019001747.7da58920.akpm@osdl.org>
> On Thu, 19 Oct 2006 00:00:27 -0700 (PDT)
> David Miller <davem@davemloft.net> wrote:
>
> > Unfortunately, the kernel has just touched the page and thus there are
> > active cache lines for the kernel side mapping. When we map this into
> > user space, userspace might see stale cachelines instead of the
> > memset() stores.
>
> hm. Has it always been that way or did something change?
Always.
> > Architectures typically take care of this in copy_user_page() and
> > clear_user_page(). The absolutely depend upon those two routines
> > being used for anonymous pages, and handle the D-cache issues there.
>
> Only anonymous pages? There are zillions of places where we modify
> pagecache without a flush, especially against the blockdev mapping (fs
> metadata).
It's cpu stores that matter, not device DMA and the like, and we have
flush_dcache_page() calls in the correct spots. You can see that
we take care of this even in places such as the loop driver :-)
--
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next prev parent reply other threads:[~2006-10-19 7:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-17 9:15 [PATCH] mm:D-cache aliasing issue in cow_user_page Dmitriy Monakhov
2006-10-19 6:33 ` Andrew Morton
2006-10-19 6:33 ` Andrew Morton
2006-10-19 7:00 ` David Miller
2006-10-19 7:00 ` David Miller, Andrew Morton
2006-10-19 7:17 ` Andrew Morton
2006-10-19 7:17 ` Andrew Morton
2006-10-19 7:22 ` David Miller [this message]
2006-10-19 7:22 ` David Miller, Andrew Morton
2006-10-19 7:41 ` Andrew Morton
2006-10-19 7:41 ` Andrew Morton
-- strict thread matches above, loose matches on Subject: below --
2006-12-05 7:38 [PATCH] mm: D-cache " Matt Reimer
2006-12-05 21:24 ` David Miller
2006-12-06 0:57 ` Matt Reimer
2006-12-06 0:59 ` David Miller
2006-12-06 7:04 ` Matt Reimer
2006-12-06 21:19 ` Matt Reimer
2006-12-07 0:46 ` David Miller
2006-12-07 6:20 ` Matt Reimer
2006-12-07 7:22 ` David Miller
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